Here are two resources to break your story and get writing:
Blake Snyder’s 15 Point Beat Sheet
Pilar Alessandra’s On the Page
Another one is to map out your story on around the hours of a clock (heard here). Tell a part of the story every 10 minutes (or less) turning it at the end of each section.
The process is the same. Start big and drill down into the details.
Now, break the story further. If you break a story into 8 pieces, break it into 10. If you break into 12, break it into 16. Structure is a tool and once you get good with a tool, break it and see how far you can push it to keep interesting for you, and more importantly, your audience.